Lower Rhine Embayment Research Articles

Dioxin-like and estrogenic activity screening in fractionated sediments from a German catchment after the 2021 extreme flood

BackgroundThe flood in July 2021 is considered one of the largest flood disasters in Western Europe in decades, with massive socio-economic consequences. The potential emission and remobilization of anthropogenic pollutants can lead to additional environmental consequences, which need to be addressed in long-term mitigation strategies. The Inde River and its tributary, the Vichtbach River, form a catchment located at the transition from the low mountain ranges of the Eifel to the lowlands of the Lower Rhine Embayment in Germany. The area has been an industrial and mining hotspot for centuries, making it a high-risk area for flood sediment pollution. The present study provides an ecotoxicological screening of flood sediments of the Vicht–Inde catchment to gain an impression of the degree of contamination by organic pollutants by means of in vitro effect-based method. Sediment samples were collected within days after the flood and fractionated prior to biotesting, and supportive instrumental geochemical analysis was performed.ResultsFlood sediments did not reveal estrogenic potential, which was included in the testing strategy as a relevant endpoint for industrial chemicals and untreated wastewater. In contrast, moderate-to-high dioxin-like activity was observed in 70% of the sediment samples with a peak dioxin-like potential at the restored section of the Inde. Overall, four hotspot samples were identified as at risk, which aligned mostly with the high concentration of organic pollutants including PAHs and PCBs. The fractionation allowed the identification of PAHs and their derivates as the most likely toxicity drivers for dioxin-like activity in the sediments of the Vicht–Inde catchment.ConclusionThe results provide first information on the prioritization of hotspot locations at risk for a detailed ecotoxicological profiling and a post-flood monitoring of organic contamination. The identified sinks of contamination in the floodplain areas can be considered a source for remobilization of pollution in future flood events, which is highly relevant for the receiving Rur River.

Loess formation and chronology at the Palaeolithic key site Rheindahlen, Lower Rhine Embayment, Germany

Abstract. The loess–palaeosol sequence and intercalated Palaeolithic find layers at the former brickyard of Rheindahlen are matters of ongoing scientific dispute. The age of different palaeosols and loess layers, hence their correlation with the global climate cycles, and the timing of repeated Neanderthal occupations have been hotly debated. These disagreements should be solved because the exceptional sedimentary and Palaeolithic sequences at Rheindahlen provide a unique opportunity to study diachronic changes in Neanderthal behaviour within the context of past climate change. We thus revisited one of the key loess sections of the Rheindahlen site to improve our understanding of loess formation processes and provide a more reliable chronostratigraphic framework for the sequence. High-resolution grain size analyses and micromorphology show that the Erkelenz Soil and the Rheindahlen Soil are characterized by more strongly developed Bt horizons than the modern soil. While these soils represent interglacial phases, the lowermost palaeosol likely formed during an interstadial and has been overprinted by weak clay illuviation during the formation of the Rheindahlen Soil. Sedimentary features of prolonged frost characterize loess and palaeosols below the modern soil and give indirect evidence for a Holocene age of the uppermost part of the sequence. Our luminescence dating approach corroborates this correlation and adds several Last Glacial deposition ages for the upper metres of the sequence. Previous correlation of this part of the sedimentary sequence with the penultimate glacial is thus rejected, whereas placing the Middle Palaeolithic inventories A3, B1, and B2 into the Last Glacial is confirmed. Luminescence measurements for the parental loess of the Erkelenz Soil and for loess layers below did not provide reliable ages probably related to signal saturation. The age of this part of the sequence thus remains open, hence the timing of human occupation testified by Palaeolithic inventories B3, B4/5, C1, and D1. The new findings provide an improved base for stratigraphic correlation of the Rheindahlen loess sequence and for investigating diachronic change in Neanderthal behaviour against the background of past climate change.

The loess landscapes of the Lower Rhine Embayment as (geo-)archeological archives – insights and challenges from a geomorphological and sedimentological perspective

Abstract. Archeological and geoscientific research in loess landscapes remains challenging due to erosional discordances and the relocation of sediments by fluvial erosion and slope wash. The Lower Rhine Embayment (LRE) can serve as a blueprint for archeological and paleoenvironmental research in loess landscapes of Central Europe. The accumulation of wind-blown dust; paleosols developed therein; and the archeological artifacts preserved in loess, colluvial or alluvial sediments are evidence of the Pleistocene and Holocene dynamics of the landscape. Geomorphologic processes in different and specific relief positions must be considered different processes that transform and relocate sediments and archeological remains. Besides aeolian accumulation, erosion and deflation have also transformed the landscape of the LRE. These include fluvial slope wash, gully formation, colluviation, and periglacial processes such as solifluction, cryoturbation and the formation of ice wedge pseudomorphs. In addition, other post-depositional processes, including weathering and soil formation, modify the sedimentary record. In light of the landscape evolution from more hilly landscapes to the flat, agriculturally used terrain we see today, we highlight the relevance and importance of different geomorphological and soil processes including their impacts and challenges for archeological and geoscientific studies.

Treatment by enhanced denitrification of forecasted nitrate concentrations under different climate change scenarios

Climate change has a decisive influence on future water resources and, consequently, on future nitrate (NO3−) concentrations. Due to decreasing water resources, in addition to decreasing and finite NO3− degradation capacities of the aquifers, higher NO3− concentrations are expected in the future. Likewise, NO3− pollution is expected to become more frequent. However, enhanced denitrification by addition of organic carbon (C) as an electron donor is a promising treatment method. This study describes the first model using NO3− projections based on climate projections, combined with the treatment method of enhanced denitrification. The exemplary study area is the Lodshof water catchment which is located in the Lower Rhine Embayment. The model illustrates the considerable potential of enhanced denitrification as an effective treatment. The expected increase in NO3− concentrations by the end of the 21st century, resulting from climate chance and a decreasing water resource, can be reduced by 38–58% in this model. In all projections, the limit value of 50 mg/L can be complied by this treatment. A projection with 20% lower NO3− input and the described treatment highlights the effectivity of combining measures to be able to manage the NO3− problem. Furthermore, this publication critically discusses the transfer of denitrification rates from laboratory experiments to the field scale and finally into models like this.

Pleniglacial dynamics in an oceanic central European loess landscape

Abstract. Loess–palaeosol sequences (LPSs) of the oceanic-influenced European loess belt underwent frequent post-depositional processes induced by surface runoff or periglacial processes. The interpretation of such atypical LPSs is not straightforward, and they cannot be easily used for regional to continental correlations. Within the last few years, however, such sequences gained increased attention, as they are valuable archives for regional landscape dynamics. In this study, the Siersdorf LPS was analysed using a multi-proxy approach using sedimentological, geochemical, and spectrophotometric methods combined with luminescence dating and tentative malacological tests to unravel Pleniglacial dynamics of the Lower Rhine Embayment. A marshy wetland environment for the late Middle Pleniglacial to the early Upper Pleniglacial was shown by colour reflectance and grain size distribution. Age inversions from luminescence dating paired with geochemical and sedimentological data reveal long-lasting erosional processes during the early Upper Pleniglacial, which were constrained to a relatively small catchment with short transport ranges. The upper sequence shows typical marker horizons for the study area and indicate harsh, cold-arid conditions for the late Upper Pleniglacial. In comparison with other terrestrial archives, the Siersdorf LPS shows that the Lower Rhine Embayment was more diverse than previously assumed, regarding not only its geomorphological settings and related processes but also its ecosystems and environments.

Hazard-informed optimization of seismic networks for earthquake early warning—the case of the Lower Rhine Embayment (western Germany)

Earthquake early warning (EEW) systems can serve as a viable solution to protect specific hazard‐prone targets (major cities or critical infrastructure) against harmful seismic events. Using the example of the Lower Rhine Embayment (western Germany), we present a novel approach for evaluating and optimizing seismic networks for EEW purposes. The network optimization is applied to simulated earthquake scenarios from a hazard-compatible stochastic catalog, which represents a realization of the seismicity in the target area over a given period of time. We propose a densification of the existing network in the area by pre-selecting a number of potential sites with an optimal station configuration using a microgenetic algorithm, minimizing an appropriate cost function associated with the network layout. We show that the new decentralized network significantly improves the warning time and the accuracy of the warnings for levels of shaking for threshold levels of at least 0.02 g. Although the accuracy of the alerts for other cities outside the target area varies depending on their location, we demonstrate that the updated network layout will also improve the warning times for neighboring cities.

Comparison of Geogases in Two Cenozoic Sedimentary Basins

We investigated fault gases (helium, radon, CO2) in two seismically active Cenozoic sedimentary basins: (a) Meinweg (in 2015), at a tectonically quiescent horst structure in the Lower Rhine Embayment; and (b) Bodanrück (in 2012; Lake of Constance), in the Molasse Basin and part of the seismically active Freiburg–Bonndorf–Bodensee Fault Zone (FBBFZ). Both study areas were selected because recent “GeoBio-Interactions” findings showed that red wood ants (RWA) are biological indicators of otherwise undetected degassing systems. We combined presence/absence data of RWA nests, their spatial pattern analysis (prototype lines), seismicity and known tectonic settings with soil gas analyses (a total of 817 samples) to unveil geochemical anomalies related to tectonic developments unknown so far. Currently, Meinweg can be considered “no ants land” due to the very low background-level of geogas concentrations. Thus, anomalies (Rn-CO2) weakly trending in NE-SW extension direction emerged. This could probably indicate the onset of (re)activation of the NE-SW-trending (Variscan) structures or the development of new fractures as an aftershock process of the 1992 Roermond earthquake that occurred about 15 km to the west. Results at Bodanrück (three RWA clusters and two RWA-free corridors) revealed degassing patterns in NW-SE and NNE-SSW directions in the clusters corresponding to re-activated and recent strike-slip fault systems. No gas anomalies were found in RWA-free corridors. The RWA nest distribution was shown to be a valuable tool for identifying areas of even actively degassing spotty anomalies caused by macro- and microscale brittle deformation masked by sediment cover.

The damaging character of shallow 20th century earthquakes in the Hainaut coal area (Belgium)

Abstract. The present study analyses the impact and damage of shallow seismic activity that occurred from the end of the 19th century until the late 20th century in the coal area of the Hainaut province in Belgium. This seismicity is the second-largest source of seismic hazard in north-western Europe after the Lower Rhine Embayment. During this period, five earthquakes with moment magnitudes (Mw) around 4.0 locally caused moderate damage to buildings corresponding to maximum intensity VII on the European Macroseismic Scale 1998 (EMS-98). Reviewing intensity data from the official macroseismic surveys held by the Royal Observatory of Belgium (ROB), press reports and contemporary scientific studies resulted in a comprehensive macroseismic intensity dataset. Using this dataset, we created macroseismic maps for 28 earthquakes, established a new Hainaut intensity attenuation model and a relationship linking magnitude, epicentral intensity and focal depth. Using these relationships, we estimated the location and magnitude of pre-1985 earthquakes that occurred prior to deployment of the modern digital Belgian seismic network. This resulted in a new updated earthquake catalogue for the Hainaut area for the 1887–1985 period, including 124 events. A comparison with other areas worldwide where currently similar shallow earthquake activity occurs suggests that intensity attenuation is strong in Hainaut. This high attenuation and our analysis of the cumulative effect of the Hainaut seismicity indicate that current hazard maps overestimate ground motions in the Hainaut area. This reveals the need to use more appropriate ground motion models in hazard issues. Another strong implication for earthquake hazard comes from the reliability of the computed focal depths that helps clarifying the hypotheses about the origin of this seismicity. Some events were very shallow and occurred near the surface up to a depth not exceeding 1 km, suggesting a close link to mining activities. Many events, including the largest shallow events in the coal area before 1970, occurred at depths greater than 2 km, which would exclude a direct relationship with mining, but still might imply a triggering causality. A similar causality can also be questioned for other events that occurred just outside of the coal area since the end of the mining works.

Denitrification in the vadose zone: Modelling with percolating water prognosis and denitrification potential

Transport and transformation processes of nitrogen in the soil are an essential part of understanding the relationship between agricultural input and nitrate (NO3−) concentrations in groundwater. The presented study describes these transformation processes around NO3− degradation at a water catchment in the Lower Rhine Embayment, Germany. Despite intensive agriculture, extracted groundwater at a depth of 21 to 22 m shows unexpectedly very low NO3− levels, below 3 mg/L NO3− for all wells. The local water supplier therefore carried out investigations in this area and generated soil data from 22 representative areas (142 soil samples from 82 drilling meters from the surface to a max. depth of 5.5 m) and groundwater analyses from 17 groundwater monitoring wells (from 3 to 5 m below ground surface). Soil types are predominantly luvisol and gleysol. The substrate in the topsoil is mainly clayey silt; underneath there are mostly medium-grained sands with partial silt intercalations which appear as a separate layer. Based on this dataset, the percolating water residence times and the NO3− leaching potential were calculated in this study. Together with the nitrogen surplus and with the help of reactive transport modelling, the denitrification potential in the vadose zone was simulated. The comparison of simulation results with laboratory-measured data shows a high correlation. Substantial NO3− reduction in the vadose zone was observed: dependent on soil type, reduction capacity and water residence time, up to 25% of the NO3− was reduced here. The applied modelling is considered an improvement in NO3− degradation potential assessment because it considers many relevant variables such as precipitation, soil parameters (grain size, field capacity, available water capacity, coarse fragments) and nitrogen input. Therefore, a transfer to other sites with comparable hydro(geo)logical conditions is possible, also due to relatively easily determinable input data. This assessment of nitrogen degradation in the vadose zone will be a useful tool for NO3− levels forecast in groundwater

Forecasting nitrate evolution in an alluvial aquifer under distinct environmental and climate change scenarios (Lower Rhine Embayment, Germany)

When investigating future nitrate (NO3−) concentrations in groundwater, climate change has a major role as it determines the future water budget and, in turn, the conditions in the aquifer which will finally have a decisive effect on NO3− concentrations. In this study, the different effects on water balance and NO3− concentration under three projected climate scenarios - RCP 2.6, RCP 4.5, and RCP 8.5 - are analysed in a water protection area in the Lower Rhine Embayment in Germany.Recharge values were calculated from downscaled precipitation and temperature data for the 21st century in a water budget that considers land use in the evapotranspiration term. Nitrate concentration evolution is estimated using recharge and expected fertilization rates with a lumped-parameter model. In order to be able to map the NO3− concentration, the investigation area is divided into 1000 × 1000 m cells. Each cell is assigned a specific NO3− input and a NO3− degradation capacity.Results show significant variations in NO3− development projected with the different climate scenarios due to different temperatures and consequently actual ET, and precipitation. Nevertheless, nitrate concentrations clearly increase in all projections. The total NO3− mass increases most strongly with RCP 8.5 until 2099 (by 89% compared to 2020) and least with RCP 4.5 (by 50%). Further projections show a 20% reduction in agricultural NO3− input can reduce NO3− concentrations, but insufficiently to comply with drinking water guidelines in all regions and aquifers. The model indicates that NO3− input loads should be defined according to future recharge variations governed by climate change. Consequently, a time-varying fertilization rate specific for each region, with their own turnover time and degradation rate, must be estimated to meet pollution environmental goals.

Seismicity in the Northern Rhine Area (1995\u20132018)

Since the mid-1990s, the local seismic network of the University of Cologne has produced digital seismograms. The data all underwent a daily routine processing. For this study, we re-processed data of almost a quarter century of seismicity in the Northern Rhine Area (NRA), including the Lower Rhine Embayment (LRE) and the Eifel Mountain region (EMR). This effort included refined discrimination between tectonic earthquakes, mine-induced events, and quarry blasts. While routine processing comprised the determination of local magnitude ML, in the course of this study, source spectra-based estimates for moment magnitude MW for 1332 earthquakes were calculated. The resulting relation between ML and MW agrees well with the theory of an ML ∝ 1.5 MW dependency at magnitudes below 3. By applying Gutenberg-Richter relation, the b-value for ML was less (0.82) than MW (1.03). Fault plane solutions for 66 earthquakes confirm the previously published N118° E direction of maximum horizontal stress in the NRA. Comparison of the seismicity with recently published Global Positioning System–based deformation data of the crust shows that the largest seismic activity during the observation period in the LRE occurred in the region with the highest dilatation rates. The stress directions agree well with the trend of major faults, and declining seismicity from south to north correlates with decreasing strain rates. In the EMR, earthquakes concentrate at the fringes of the area with corresponding the largest uplift.

Patterns in river channel sinuosity of the Meuse, Roer and Rhine rivers in the Lower Rhine Embayment rift-system, are they tectonically forced?

The tectonic and fluvial setting of the Rhine-Meuse river system in the Lower Rhine Embayment rift system is exceptionally well known. The 19th century, pre-regulation river courses of three rivers are used to study a postulated sinuosity response to faulting. The fault-perpendicular Meuse River shows patterns of sinuosity changes at different spatial scales. The large-scale (>5 km) sinuosity changes are related mainly to the faulting-induced changes of the subsurface lithology, determining the bed and bank characteristics. However, at a smaller scale, some fault-related channel sinuosity anomalies are observed. The fault-parallel Roer River shows sinuosity changes related to a normal, non-tectonic longitudinal gradient change. Sinuosity patterns of the Rhine River are predominantly related to lithological differences and reduced incision rates. Sinuosity can thus be an indicator of tectonic motions, but gradient, subsurface lithology and river bank composition determine sinuosity as well. Therefore, a sinuosity change is no proof for fault activity. On the other hand, the absence of a sinuosity change does not imply inactivity of a fault at geological time-scales.

Regional broad-band ground-shaking modelling over extended and thick sedimentary basins: an example from the Lower Rhine Embayment (Germany)

The simulation of broad-band (0.1 to 10 + Hz) ground-shaking over deep and spatially extended sedimentary basins at regional scales is challenging. We evaluate the ground-shaking of a potential M 6.5 earthquake in the southern Lower Rhine Embayment, one of the most important areas of earthquake recurrence north of the Alps, close to the city of Cologne in Germany. In a first step, information from geological investigations, seismic experiments and boreholes is combined for deriving a harmonized 3D velocity and attenuation model of the sedimentary layers. Three alternative approaches are then applied and compared to evaluate the impact of the sedimentary cover on ground-motion amplification. The first approach builds on existing response spectra ground-motion models whose amplification factors empirically take into account the influence of the sedimentary layers through a standard parameterization. In the second approach, site-specific 1D amplification functions are computed from the 3D basin model. Using a random vibration theory approach, we adjust the empirical response spectra predicted for soft rock conditions by local site amplification factors: amplifications and associated ground-motions are predicted both in the Fourier and in the response spectra domain. In the third approach, hybrid physics-based ground-motion simulations are used to predict time histories for soft rock conditions which are subsequently modified using the 1D site-specific amplification functions computed in method 2. For large distances and at short periods, the differences between the three approaches become less notable due to the significant attenuation of the sedimentary layers. At intermediate and long periods, generic empirical ground-motion models provide lower levels of amplification from sedimentary soils compared to methods taking into account site-specific 1D amplification functions. In the near-source region, hybrid physics-based ground-motions models illustrate the potentially large variability of ground-motion due to finite source effects.

The Diest Formation: a review of insights from the last decades

Research conducted since the 1960s on the upper Miocene Diest Formation in NE Belgium is reviewed and integrated. Their lithology unites the deposits of the glauconiferous Diest Sand in one formation, though biozones and internal sedimentary structures strongly suggest the formation may agglomerate the deposits of two separate, successive sedimentary cycles. The lowermost cycle is thought to have deposited the "Hageland Diest sand" during the early or middle Tortonian. It contains the Diest Sand in the main outcrop area in Hageland, Zuiderkempen and central Limburg, and probably also the Deurne Member near the city of Antwerpen. It furthermore includes the lower part of the Dessel Member in the central Kempen and in the Belgian part of the Roer Valley Graben (RVG). The Hageland Diest cycle represents the infill of a large tidal inlet tributary to the southern North Sea bight, then situated over the southern Netherlands and the Lower Rhine embayment. The Hageland Diest sand has the composition of a marine deposit, yet the confined area of occurrence and the presence of tens of metres deep incisions at the base, set it apart. The confinement of the embayment, strong tides and a steady supply of coastal‐marine sand are invoked as the main driving forces that resulted in the distinctive geometry and internal architecture of the unit. The upper cycle is associated with the "Kempen Diest sand", which is found in the subsurface of the RVG and the Noorderkempen. It has a late Tortonian to earliest Messinian age with progressively younger ages occurring to the NW. It encompasses the upper part of the Dessel Member and the overlying, coarser Diest Sand, and correlates to most or all of the thickly developed Diessen Formation in The Netherlands. It is the deposit of a prograding marine delta, containing both marine components and continental components fed by the palaeo‐Meuse/Rhine river mouths. Accommodation space kept increasing during deposition, due to subsidence of the deposition area, especially inside the RVG but also in the Noorderkempen. Although there is a fair consensus on the above, many concrete points about the geometry and depositional history of the Diest Formation and even a definitive decision on its single or dual character remain to be sorted out. In addition, this review excludes the Flemish Hills sand and the Gruitrode Member from the Diest Formation.

Geodetic evidence for a buoyant mantle plume beneath the Eifel volcanic area, NW Europe

SUMMARY The volcanism of the Eifel volcanic field (EVF), in west-central Germany, is often considered an example of hotspot volcanism given its geochemical signature and the putative mantle plume imaged underneath. EVF's setting in a stable continental area provides a rare natural laboratory to image surface deformation and test the hypothesis of there being a thermally buoyant plume. Here we use Global Positioning System (GPS) data to robustly image vertical land motion (VLM) and horizontal strain rates over most of intraplate Europe. We find a spatially coherent positive VLM anomaly over an area much larger than the EVF and with a maximum uplift of ∼1 mm yr−1 at the EVF (when corrected for glacial isostatic adjustment). This rate is considerably higher than averaged over the Late-Quaternary. Over the same area that uplifts, we find significant horizontal extension surrounded by a radial pattern of shortening, a superposition that strongly suggests a common dynamic cause. Besides the Eifel, no other area in NW Europe shows significant positive VLM coupled with extensional strain rates, except for the much broader region of glacial isostatic adjustment. We refer to this 3-D deformation anomaly as the Eifel Anomaly. We also find an extensional strain rate anomaly near the Massif Central volcanic field surrounded by radial shortening, but we do not detect a significant positive VLM signal there. The fact that the Eifel Anomaly is located above the Eifel plume suggests that the plume causes the anomaly. Indeed, we show that buoyancy forces induced by the plume at the bottom of the lithosphere can explain this remarkable surface deformation. Plume-induced deformation can also explain the relatively high rate of regional seismicity, particularly along the Lower Rhine Embayment.

Sand injectites: from source to emplacement – an example from the Miocene age Frimmersdorf Seam, Garzweiler Open-cast Mine, Lower Rhine Embayment

Abstract Sand injectites are reported from a Miocene-age lignite seam in the Lower Rhine Embayment, which is exploited in the Garzweiler open-cast mine, Germany. Owing to the ongoing mining of the seam, the sand injectite morphology and extent were documented over a 3 year period. The combination of fieldwork, geophysical and drilling well data, as well as a 3D reconstruction of the host unit, reveal that the sand injectites within the Frimmersdorf Seam (= host unit) are highly variable, and include sills, dykes, reticulate (i.e. an interconnected network of thin sand veins) and irregular-shaped sand bodies. The injectites are connected to the underlying Frimmersdorf Sand or the overlying Neurath Sand (= parent sand units), or can be distributed throughout the seam. The differentiation of sand injectites from syn-depositional sand bodies is based on the orientation (discordant/concordant) and the presence of primary sedimentary structures in the latter. The prevailing stress field across the Lower Rhine Basin, and the coeval nature of fault activity, controlled the formation of sand injectites in the region. While such structures have been noted for over 30 years, this study is the first to provide a detailed analysis of these economically important features, including their classification, extent and morphology.

The Roman Eifel Aqueduct: archaeoseismological evidence for neotectonic movement at the transition of the Eifel to the Lower Rhine Embayment

The Lower Rhine Embayment and adjacent areas are characterised by neotectonic deformation resulting in differential crustal movement. Slip rates along the fault systems are very low (< 0.1 mm/a). Significant earthquakes are known to have occurred in the past but the faulting behaviour is not adequately known which hampers the risks assessment. We analysed the archaeological record of the largest Roman aqueduct north of the Alps. This so called Eifel Aqueduct is 95.4 km long, has its source in the Eifel mountains and supplied the ancient city of Cologne with calcareous fresh water. The aqueduct crosses major faults of the Lower Rhine Embayment perpendicular. Analyses of the aqueduct´s gradient gives weak evidence for creep along the Kirspenich Fault resulting in differential movement of hanging and foot wall in the order of a few centimetres. Vertical offsets of 15 and 35 cm are documented exactly where the aqueduct crosses the Holzheim Fault system close to the city of Mechernich. Here, also structural damage of the aqueduct is recorded and archaeological evidence exists for repair works on the aqueduct. We interpret these observations as well as the construction of a 4 km long deviation as necessary measures to keep the aqueduct operational after earthquake damage. The timing of the event falls within the period of aqueduct operation which is reconstructed to be between 80 ± 10 and 270 ± 10 CE. Supporting evidence for earthquake activity within this period is seen in the roof collapse of the nearby Kakus cave.

Long-term effects of mining-induced subsidence on the trapping efficiency of floodplains

Abstract Effects of human activities such as land-use changes, flood protection measures, coal-mining activities, and urbanization on river-floodplain systems are widespread and have been well known to extensively change the hydro- and morphodynamics of rivers. Land subsidence, e.g., that caused by the extraction of coal in subsurface mining tunnels in riverine environments, results in local or large-scale ground-surface irregularities where sediment is eroded or deposited during flooding. This study determined the long-term effects of mining-induced subsidence on the trapping efficiency of floodplains. The Wurm River (Lower Rhine Embayment, Germany) provided a test case owing to its central location in a previous underground coal-mining region. To analyze the effects of mining subsidence on the trapping efficiency of floodplains, we developed a numerical model based on the Delft3D software that applied the embedded space-varying subsidence module. The time series for the space-varying changes of the surface elevation were defined on a computational grid. Results of nine scenarios showed that subsidence led to a local increase in the silt trapping efficiency on floodplains when subsidence generally increased the frequency and magnitude of floodplain inundation, and acted as a local trap for sediment. The model developed in this study is applicable to rivers with similar characteristics, such as small meandering rivers with large floodplains, where suspended sediment accounts predominantly for the deposition on floodplains.

New age constraints for the Saalian glaciation in northern central Europe: Implications for the extent of ice sheets and related proglacial lake systems

A comprehensive palaeogeographic reconstruction of ice sheets and related proglacial lake systems for the older Saalian glaciation in northern central Europe is presented, which is based on the integration of palaeo-ice flow data, till provenance, facies analysis, geomorphology and new luminescence ages of ice-marginal deposits. Three major ice advances with different ice-advance directions and source areas are indicated by palaeo-ice flow directions and till provenance. The first ice advance was characterised by a southwards directed ice flow and a dominance of clasts derived from southern Sweden. The second ice advance was initially characterised by an ice flow towards the southwest. Clasts are mainly derived from southern and central Sweden. The latest stage in the study area (third ice advance) was characterised by ice streaming (Hondsrug ice stream) in the west and a re-advance in the east. Clasts of this stage are mainly derived from eastern Fennoscandia. Numerical ages for the first ice advance are sparse, but may indicate a correlation with MIS 8 or early MIS 6. New pIRIR290 luminescence ages of ice-marginal deposits attributed to the second ice advance range from 175 ± 10 to 156 ± 24 ka and correlate with MIS 6.The ice sheets repeatedly blocked the main river-drainage pathways and led to the formation of extensive ice-dammed lakes. The formation of proglacial lakes was mainly controlled by ice-damming of river valleys and major bedrock spillways; therefore the lake levels and extends were very similar throughout the repeated ice advances. During deglaciation the lakes commonly increased in size and eventually drained successively towards the west and northwest into the Lower Rhine Embayment and the North Sea. Catastrophic lake-drainage events occurred when large overspill channels were suddenly opened. Ice-streaming at the end of the older Saalian glaciation was probably triggered by major lake-drainage events.

Landscape instability at the end of MIS 3 in western Central Europe: evidence from a multi proxy study on a Loess-Palaeosol-Sequence from the eastern Lower Rhine Embayment, Germany

The Lower Rhine Embayment hosts important Loess-Palaeosol-Sequences (LPS) within the western European loess belt yielding valuable information on landscape evolution and palaeoclimatic dynamics. The study focusses on the palaeoenvironmental development based on a LPS from the eastern shoulder of the Lower Rhine Embayment (Düsseldorf-Grafenberg). The palaeoenvironmental development within the study area is presented and discussed based on high-resolution grain size analyses, selected environmental magnetic parameters, and geochemical analyses complemented by luminescence age estimates. Differences in grain size distribution (ΔGSD) as well as the U-ratio clearly reflect main stratigraphical units within the LPS. In addition, the centered-log-ratio transformation of ΔGSD (ΔGSDclr), which is sensitive to post-depositional grain size variations, traces units of intensified soil formation. Despite no magnetic enhancement can be observed within the Grafenberg LPS, environmental magnetic parameters combined with selected geochemical analyses (Sr/Rb) provide direct information on the modification of silicates and magnetic minerals in the course of pedogenesis and diagenesis. Overall, the Grafenberg LPS contributes to the understanding of environmental conditions within the Lower Rhine Embayment particularly for the late MIS 3 and the transition to MIS 2. The LPS reflects major shifts in the geomorphic system, which are compared to palaeoenvironmental records from different archives and different geographic regions in north-western Europe indicating a direct relation to North Atlantic Climate oscillations during the last glacial period. It is shown that the Hesbaye unconformity (at the MIS 3/2 boundary) is bound to an erosional event, which can be traced over wide areas within the northern European loess belt.